The science

Holiday weight gain: what an NIH study actually measured

Every autumn the same warning comes round: the average person puts on five pounds or more between Thanksgiving and New Year. When researchers at the US National Institutes of Health went looking for the data behind that claim, they found very little — so they weighed people themselves. The real number was much smaller. The part worth remembering is what happened afterwards.

What the scale showed

The average gain across the holiday period was 0.37 kg — about 0.8 lb. That was the only one of the three periods with a statistically significant change: the pre-holiday weeks showed an average gain of 0.18 kg that could have been chance, and the post-holiday weeks a 0.07 kg loss that was not significant either.

In other words, the holiday gain was small, and it did not go away. The authors concluded that because it is not reversed during spring or summer, this modest fall-and-winter gain probably contributes to the slow increase in body weight that often happens across adulthood. Half a kilo a year is easy to dismiss in any single winter; it is harder to dismiss over a decade.

The average hides a spread

An average of under a pound does not mean everyone gained under a pound. According to the NIH's summary of the findings, fewer than 10% of participants gained more than five pounds over the holidays, and those who were already overweight or had obesity were more likely to be in that group. Some people lost weight.

The same summary notes that only two of the factors the team looked at were linked to smaller gains (or losses): reporting more physical activity, and reporting less hunger. And when asked, participants believed they had gained about three pounds more than the scale showed — a reminder that how heavy we feel after a big week of eating and what the trend is actually doing are not the same thing.

What the study does not tell you

This was a convenience sample of US adults measured over a single season, not a nationally representative survey, and it was designed to measure weight change rather than to test any intervention. It describes what happened to an average group of volunteers; it does not predict what will happen to any individual, and it says nothing about what anyone should eat. Other countries' holiday calendars differ, and so may the timing of their seasonal gains.

What this means for watching your own trend

• ✓A single heavy morning after a holiday meal is mostly noise — food and water still in transit. The question that matters is whether the trend has moved, and that takes a few weeks of weigh-ins to answer.
• ✓The change worth noticing is small. Half a kilo is well inside normal day-to-day fluctuation, which is why it can slip past unnoticed unless you look at a smoothed line rather than individual readings.
• ✓Look again in February or March. In this study, that was when the net seasonal change had settled — and it stayed put through the following year.
• ✓Your own guess is not a reliable gauge. Participants overestimated their gain; a weigh-in history gives you the real number in either direction.

Sources

1. Yanovski JA, Yanovski SZ, Sovik KN, Nguyen TT, O'Neil PM, Sebring NG. A prospective study of holiday weight gain. The New England Journal of Medicine. 2000;342(12):861–867. doi:10.1056/NEJM200003233421206 (PMID 10727591; full text free at PMC4336296).
2. National Institute of Child Health and Human Development. Holiday weight gain slight, but may last a lifetime. NIH news release, March 22, 2000. nichd.nih.gov.

This article is general information about published research. It is not medical, nutritional, or diagnostic advice, and it is not a recommendation for any individual. Talk to a qualified healthcare professional about your own circumstances.

More LyteFast articles  ·  Weigh-in frequency and the trend line  ·  Why weight loss slows  ·  Research behind the app